This invention relates to a color filter and a fluorescent display device having color filters incorporated therein.
There has been conventionally known a fluorescent display device which is adapted to carry out a full-color luminous display by means of color filters, which is generally constructed in such a manner as shown in each of FIGS. 5(a) and 5(b). More particularly, a conventional fluorescent display device generally designated at reference numeral 100 in each of FIGS. 5(a) and 5(b) includes an anode substrate 101 on which a display section is provided as described hereinafter.
The fluorescent display device 100 includes an airtight envelope, of which a part is constituted by the anode substrate 101 made of a light-permeable insulating material. The anode substrate 101 is provided on an inner surface thereof with three kinds of strip-like color filters 102, 103 and 104 of red, green and blue colors R, G and B in turn in a repeated manner and so as to be contiguous to each other without defining any gap therebetween. The color filters 102 to 104 each are provided thereon with a strip-like light-permeable anode conductor 105, as shown in FIG. 5(a). Alternatively, each of the color filters 102 to 104 may be provided thereon with a strip-like light-permeable anode conductor 105 formed with openings 108, as shown in FIG. 5(b). The anode conductors 105 each have a strip-like phosphor layer 106 deposited thereon. Thus, the strip-like phosphor layers 106 cooperate with the strip-like anode conductors 105 to form a plurality of strip-like anodes 107 arranged in parallel to each other so as to be spaced from each other at predetermined intervals. A phosphor material of the same kind is commonly used for the phosphor layers. For example, a ZnO:Zn phosphor material having a luminous spectrum of a wide range extending from a blue luminous color to a red luminous color with a green luminous color being interposed therebetween may be conveniently used for the phosphor layers.
The fluorescent display device also includes control electrodes and electron emitting cathodes (not shown) each constructed in a predetermined structure and arranged above the strip-like anodes 107 arranged in a stripe-like manner, which cooperate with the anodes 107 to form a drive matrix. Matrix driving of the fluorescent display device 100 thus constructed permits a selected portion of the phosphor 106 of each of the anodes 107 to emit light of a green luminous color, which then passes through the color filters 102 to 104 and light-permeable anode substrate 101, to thereby be provided with colors of the color filters separately.
In formation of the color filters described above, a color filter material is prepared for every desired color by mixing a frit glass powder with a pigment exhibiting each of desired colors. Subsequently, the color filter materials for the respective desired colors are applied to the anode substrate 101 in turn and in a repeated manner by printing and then dried, followed by calcination in a lump.
As will be noted from the above, the color filters each are formed by subjecting a color filter material mainly consisting of inorganic materials to calcination, so that considerable roughness or unevenness is formed on a surface of each of the color filters. Thus, it is highly difficult to form the color filters into a flat configuration on the anode substrate.
Unfortunately, this causes formation of the anode conductors at pitches as fine as, for example, 1 mm on the color filters thus formed to be highly difficult and troublesome. Also, it causes formation of each of the anode conductors in a manner of permitting it to exhibit a uniform resistance to be extensively difficult. Use of an ITO film for the anode conductors causes them to be formed into an extensively reduced thickness, so that a resistance of each of the anode conductors is highly affected by or varied depending on unevenness on the surface of the color filters. Also even use of an aluminum film for the anode conductors likewise causes a resistance of each of the anode conductors to be increased due to unevenness of the color filters, resulting in the anode conductors being often broken.
Alternatively, the anode conductors each may be formed by etching so as to be arranged in a stripe-like manner. However, a chemical agent or etching liquid used for the etching often leads to problems such as deterioration of the color filters, formation of further unevenness on the surface of the color filters, breaking of the anode conductors due to melting, and the like.